Known forced-air burners for liquid or/and gaseous fuels (e.g. in accordance with DIN EN 267/676 or DIN EN 746), in particular what are called monobloc burners, are normally attached suspended to a combustion chamber (e.g. boiler) or a combustion chamber housing demarcating said chamber. It is customary to locate the forced-air burner on the combustion chamber housing or by way of a module interposed therebetween which is used to introduce fuels.
Forces arising In the attached position, in particular weight, and forces arising when the forced-air burner is operating, are transferred through the housing for the forced-air burner into the combustion chamber housing. The same applies to moments arising in the attached state and during operation.
Accordingly, the housing for the forced-air burner must be designed as a whole with respect to its mechanical durability to absorb forces and moments from the forced-air burner; it is not sufficient just to consider the burner housing in isolation. The module must also be designed accordingly when using a module located between the forced-air burner and the combustion chamber housing.
When designing the burner housing, or the module, special attention must be paid to the blower motor, the fan impeller, the induction plenum with the throttle valve, electronic components, hydraulic components and mechanical combination regulator in particular because of their mass.
If the housing is thought of as an air ducting device, the dead weight of the housing increases with increasing air capacity. With increasing air capacity, which can be considered as correlated to firing capacity, the mass of the components enclosed by and attached to the housing increases further. Specific components in particular, such as for example, the blower motor and the fan impeller, contribute in particular to the increase in mass of the forced-air burner as a whole. The consequence is that the ratio of the component mass of a forced-air burner without its housing to the mass of the burner housing becomes greater, the higher the air capacity, or the firing capacity.
In order to take account of the increased forces and moments arising in the forced-air burner with increasing air capacity, or firing capacity, the design complexity with respect to the housing has to be increased accordingly. Sometimes complex calculations are required, for example, to determine mechanical stresses in the housing. The materials used for the housing have to be dimensioned accordingly, for example, provided with suitable wall thicknesses to meet the increased requirements for mechanical durability.
A further disadvantage of known burner layouts is that to obtain access to a module located between the burner and the combustion chamber housing or mixing device it is necessary to swing the burner away completely from the module, or the burner together with the module away from the combustion chamber housing. To do this, hinges are employed which are attached to the burner and the module, or to the module and the combustion chamber housing. These hinges have to sustain the forces and moments generated during the swinging motion, caused in particular by the heavy burner housing. There is no possibility of designing the combustion chamber housing to allow access to the module, or the mixing device, because of the above requirement for the combustion chamber housing regarding the absorption of forces and moments.
One well-known approach to solving this problem consists of diverting the forces and moments generated by the forced-air burner vertically downward into the ground. A trestle is normally used for this, which is mounted on the floor and attached to the frame of the forced-air burner. Specifically, it is customary to attach the blower motor of the forced-air burner to the frame, while the additional components of the forced-air burner are located on the motor. What this achieves is that the design for the housing only needs to take the mass of the housing into consideration with respect to mechanical durability. This approach, which is known from the field of fans, has the disadvantage that a plurality of trestles of different heights has to be provided for different installation heights, for example, depending on the type of boiler. Furthermore, it is necessary when using this procedure to ensure that the trestle, or the forced-air burner mounted on it, is decoupled from the vibrations of the combustion chamber or the combustion chamber housing. Otherwise because of the vibration loop from forced-air burner to combustion chamber housing to floor to forced-air burner, damage may result to the trestle, the forced-air burner and the combustion chamber housing and to other components involved in the vibration loop.